The availability of flexible photovoltaic and piezoelectric materials, coupled with increasing pressures to efficiently capture energy from renewable sources, makes the use of both piezoelectric and photovoltaic technologies, simultaneously and/or at the same location, an increasingly attractive possibility. A hybrid structure comprising both technologies may be deployed to harvest energy both from solar energy and from mechanical energy sources such as rain, wind, waves, or tides. A flexible piezoelectric polymer may be used to harvest mechanical energy and at the same time may act as a substrate material for organic photovoltaic cells.
WO 2009/070706 describes the use of flexible organic solar cells for artificial turf to generate solar energy. The use of such a system would be limited by the availability of sunlight to certain periods of the day. The structure specified in the above patent is incapable of using mechanical energy.
U.S. Pat. No. 7,705,523 B2 describes a hybrid device using dye-sensitised solar cells and zinc oxide (ZnO) piezoelectric nano-rods for converting both solar and mechanical energy to electrical energy. The hybrid structure can be developed only in the form of fibres, but not as films or sheets. Films or sheets may be desirable in certain applications, for example, in energy harvesting where mechanical energy from water or wind is converted to electricity. The hybrid structure described in U.S. Pat. No. 7,705,523 B2 may not be modified to accommodate other kinds of less expensive solar cells, such as organic solar cells or amorphous silicon solar cells. The structure is also highly complex, featuring a hierarchical structure including tubules with radiating nano-rods. A simplified structure is desirable both for enabling simpler production methods and for allowing the use of such hybrid piezoelectric-photovoltaic technologies at different scales and in different structural forms, such as in the form of films or sheets, as well as fibres.
An aim of embodiments of the present invention is therefore to provide an improved method of storing, consuming, and/or generating electrical energy scavenged from both solar and mechanical sources. Another aim of embodiments of the invention is to provide an improved power generation system for harvesting both solar and mechanical energy for use with such a method. A further aim of embodiments of the present invention is to provide a hybrid structure having piezoelectric and photovoltaic characteristics for use in such a system. Yet another aim of embodiments of the invention is to provide a method for making such a structure.